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Need Help With Cabinet Design

Discussion in 'Amps and Cabs [BG]' started by Sidecar666, May 6, 2005.

  1. Sidecar666


    Mar 27, 2004
    Ok...I've got an Eminence Omega Pro-15 Woofer (15"-8 ohm) and a box that is 24.5x24x16" internal dimensions. This gives me 5.44 ft cubed of volume (by my math...which sucks! :smug: ). I've put a 6" long x 6" diameter port into the cab and the sound just isn't very deep...it's kinda weak. Phase is all good and the cab is sealed up well. Can anyone give me a clue on what I'm doing wrong? Here's some T-S specs for the woofer:
    Fs-39 Hz, Qes-.36, Qms-8.57, Qts-.35, Vas-6.92 cu.ft.(196 L), Xmax-4.8mm, Sensitivity-99dB, RMS power-800 Watts.
    Maybe someone with a good box calculator can suggest something?
    For more specs on the woofer go to www.usspeaker.com
  2. Sidecar666


    Mar 27, 2004
  3. The woofer you used is designed for a very small box; smaller than you made (about half the volume you used). For this they sacrificed some efficiency. This driver probably is only usable as a subwoofer, not for a stand-alone bassguitar cab.
    Have you calcutated the port?
  4. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Assuming your math is correct (and I didn't check it) you tuned the box to about 38Hz. That's too low, and you have falling response below 100 Hz. Make the vent 2" long and you'll get a response bump around 60Hz that will return the bass.
  5. I guess it's the efficiency that is the problem here: it is 2 db less loud as your avarage cab. This would make it sound weak next to other cabs. The driver is meant to be used in a PA-subwoofer with a VERY powerfull amp driving it: they sacrificed efficiency for portability designing this driver. This is not a problem as long as you have the power to drive it (it really needs the 800 watts going into it; if you have less watts you are better of with a more efficient driver).
  6. I didnot check the math either, but if he tuned to 38 hz you are certainly right suggesting a higher tuning frequency.
  7. Sidecar666


    Mar 27, 2004
    Wow...1/2 the volume of what I made? Dang...here comes the sawzall!!! Will a tuning frequency of 60Hz make the thing not sound deep enough? Would I be better off just selling off the woofer and getting a more efficient one? I thought 99 dB was pretty efficient. hmmmmmm :meh:
  8. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    Avatar. :eek: ;)
  9. I have it listed here as 97Db...
    And Billfitzmaurice did not say tune @ 60 Hz, he suggested a certain port length... with this port lenght your tuning is higher than 38Hz but he did not specify the tuning frequency.
    With your cab size i suggest you'd be better off buying either another driver or another one of the omega pro 15 and make it a 2x15 (tune between 50 and 55 Hz would be my suggestion with this driver but i am not an expert).
  10. I think i would recommend Eminence Kappa 15 LF for this cabinet (a +/- 150 liter 1x15); tuned between 50 and 55 Hz.
  11. Sidecar666


    Mar 27, 2004
    I already have an Avatar 2x10 and a 4x10. was looking for a bit more meat for them potatos to sing with! :D
  12. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    With your existing box a 2" duct will tune it to about 50Hz and all should be fine. I wouldn't make a smaller box unless you really want one. With the mod I suggested you'll be flat to about 90 Hz, with a 1dB bump below that, then response will drop below average SPL at 55Hz with f3 at 46 Hz. Make the box the 'ideal' net 3.6 cu ft net volume and response will fall off below 80 Hz with f3 at 52 Hz.

    You could have figured this out yourself in less than a minute with WinISD, and since the program is free one wonders why you didn't do so before buying the driver and building the box. No offense intended, but that's a lot of money to spend without doing your homework first. It's pure **** luck that you didn't end up with something that you couldn't use.

    link wray is correct that this driver has specs and capabilities not usually seen in drivers used for bass. It's a lot better. I wouldn't change it or the box, just cut the port to the right size. You should consider adding an Alpha 8MR crossed over at 800 to 1.2kHz to get some midrange response and dispersion.
  13. Sidecar666


    Mar 27, 2004
    The speaker was given to me by a freind who does sound reinforcement. I have a macintosh computer that doesn't run any of the software that you all seem to have. I've done a search and a post on getting software for Mac. No luck. The cabinet I used was from an old JBL speaker I had that was blown. I figured I'd try it out with the limited resources I had...Thanks for your help and assumptions
  14. yeah, i´ve been looking for that myself. l´m "lucky" to have an old, old pc collecting dust...
  15. I've got a Delta 15 that I use in a cabinet about 16 x 18 x 12. It seems to work fine and is very snappy. I'm going to put this in another closed back cab about the same size as my 4 x 10. Then I'm going to experiment with closing the port on the 4x10 to see if that cuts some of the boomyness I seem to get.

    In the olds days of the 60's when I started, all the bass cabs from Marshall were closed and the usual set up was 2 cabs of 4 x 12 with one 50 watt amp. As these speakers were only rated about 25 watts each, you can see how much louder we can get now, and why big concerts had huge stacks of cabs on each side of the stage in the 60's. (Those were the days.......no foldback, no sound-man, no road crew, one van between all of us and no cars. Avergae gig - two bands - one hour on and off twice - 4 hours of rock and blues).
  16. Download my spread sheet from my signature, and find the Omega Pro 15 entry. All the math is done for you, so all you have to do is pick your favorite alignment.

    I prefer SBB4 for tighter bass, but at some expense to bottom end.

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